Abstract: We extend the definition of the recently introduced valence bond entanglemententropy to arbitrary SU2 wave functions of S=1-2 spin systems. Thanks to areformulation of this entanglement measure in terms of a projection, we areable to compute it with various numerical techniques for frustrated spinmodels. We provide extensive numerical data for the one-dimensional J1-J2 spinchain where we are able to locate the quantum phase transition by using thescaling of this entropy with the block size. We also systematically comparewith the scaling of the von Neumann entanglement entropy. We finally underlinethat the valence-bond entropy definition does depend on the choice ofbipartition so that, for frustrated models, a -good- bipartition should bechosen, for instance according to the Marshall sign.